Method of manufacturing solid state imaging device, solid state imaging device, and camera using solid state imaging device

ABSTRACT

A method of manufacturing a solid state imaging device having a photo-electric conversion portion array and a transfer electrode array, these arrays being provided in parallel to each other, upper surfaces and side wall surfaces of the transfer electrode array being covered with a light-shielding layer, and a transparent layer showing an oxidizing property at the time of film formation, the transparent layer being formed on the photo-electric conversion parts and the light-shielding layer.

CROSS REFERENCES TO RELATED APPLICATIONS

The subject matter of application Ser. No. 11/511,643, is incorporatedherein by reference. The present application is a Divisional of U.S.Ser. No. 11/511,643, filed Aug. 29, 2006, which claims priority toJapanese Patent Application JP2005-275823 filed with the Japanese PatentOffice on Sep. 22, 2005, and Japanese Patent Application JP2005-256694filed with the Japanese patent Office on Sep. 5, 2005 the entirecontents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a solid stateimaging device, the solid state imaging device, and a camera using thesolid state imaging device.

2. Description of the Related Art

CCD solid state imaging devices used for area sensors and the like havea configuration in which a photo-electric conversion portion arrayincluding a plurality of photo-electric conversion parts and a transferelectrode array including a plurality of transfer electrodes arearranged in parallel to each other on a semiconductor substrate. Thetransfer electrode array is disposed on charge transfer paths formed inthe semiconductor substrate, and the plurality of transfer electrodesare sequentially driven, whereby charges are transferred along thecharge transfer paths.

Particularly, in a CCD solid state imaging device of the inter-transfertype, the transfer electrode array is covered with a light-shieldinglayer to prevent light from being incident on the charge transfer paths.The light shielding by the light-shielding layer is for preventing thesmear phenomenon, i.e., the appearance of a line on a screen through achange in the amount of charges being transferred, which would occur iflight is incident on the charge transfer path during transfer of acharge sequentially to the lower side of the transfer electrode in theadjacent pixel in a CCD solid state imaging device. As the material ofthe light-shielding layer, in general, such a metallic material asaluminum, tungsten and molybdenum is used. For forming thelight-shielding layer, a light-shielding layer material layer is formedby sputtering or CVD on the semiconductor substrate provided with thephoto-electric conversion parts and the transfer electrode array. As aresult, the light-shielding layer material layer is formed not only onthe upper surfaces and side wall surfaces of the transfer electrodearray to be light-shielded but also on the surfaces on thephoto-electric conversion parts. Subsequently, therefore, thelight-shielding material on the photo-electric conversion parts isremoved by etching so that the photo-electric conversion parts come tobe able to receive light. A solid state imaging device having this kindof light-shielding layer is described, for example, Japanese PatentLaid-open No. Hei 10-178166.

SUMMARY OF THE INVENTION

The light shielding performance of a light-shielding layer is determinedby the extinction coefficient of the material of the light-shieldinglayer and the thickness of the light-shielding layer. As the extinctioncoefficient of the material used is higher, the film thickness can bemade smaller advantageously. At present, metallic materials such asaluminum, tungsten and molybdenum are generally used as the material ofthe light-shielding layer in CCD solid state imaging devices, and thesemetallic materials are known to have high extinction coefficients forvisible rays. A light-shielding layer formed of tungsten may need a filmthickness of around 200 nm in order to attain a light shieldingperformance for attenuating visible rays to −100 dB.

The photo-electric conversion parts in a CCD solid state imaging deviceare formed in valleys between large-height transfer electrodes on asemiconductor substrate. Of the transfer electrode array, both the uppersurfaces and the side wall surfaces are covered with the light-shieldinglayer. Therefore, if the light-shielding layer is larger in thickness,the side wall surfaces of the transfer electrode array are bulged moreaccordingly, and the width of the valleys between the transferelectrodes becomes smaller. As a result, the aperture area of thephoto-electric conversion parts is reduced, leading to a lowersensitivity. This is the reason for the fact that a light-shieldinglayer is more advantageous as its thickness is smaller. In addition, areduction in the thickness of the light-shielding layer is importantalso for pursuing a further miniaturization of the solid state imagingdevice. Accordingly, it is desired to use a film material with a higherextinction coefficient as the material of the light-shielding layer.

As a material further higher than tungsten in extinction coefficient,ruthenium and iridium are known. For light with a wavelength region inthe vicinity of 700 nm, tungsten has an extinction coefficient of 2.78to 2.91, whereas ruthenium has 4.45 to 4.22 and iridium has 4.81 to4.92. Thus, ruthenium and iridium are higher than tungsten in extinctioncoefficient by about 60%; therefore, when ruthenium or iridium is used,the thickness of the light-shielding layer can be reduced by about 60%,as compared with the case of using tungsten.

However, in the CCD solid state imaging device, after the formation ofthe light-shielding layer, a transparent layer composed of boronphosphorus silicate glass (BPSG) or phosphorus silicate glass (PSG) isformed thereon, for the purpose of forming a waveguide path or a lens.The BPSG film and the PSG film are transparent layers which show anoxidizing property at the time of film formation; particularly, thesefilms show a strong oxidizing property in a heating reflow step includedin the film forming process. On the other hand, ruthenium and iridiumare materials liable to be oxidized; therefore, when the light-shieldinglayer is formed by use of ruthenium or iridium, the metallic materialwill be easily oxidized at the time of forming the transparent layerthereon. Particularly, when ruthenium (Ru) is converted into its oxide(RuOx), the extinction coefficient is lowered as compared with that ofthe elemental ruthenium, so that it becomes difficult to obtain theexpected light shielding performance. In addition, part of ruthenium maybe converted into volatile ruthenium tetroxide (RuO₄) and be evaporated,with also leads to local thinning of the light-shielding layer,accompanied by a lowering in light shielding performance at the thinnedportion and a worsening of the smear characteristic.

Thus, there is a need to prevent a light-shielding layer from beingoxidized at the time of forming a transparent layer, in manufacturing asolid state imaging device in which a photo-electric conversion portionarray including a plurality of photo-electric conversion parts and atransfer electrode array including a plurality of transfer electrodesare provided in parallel to each other, the upper surfaces and side wallsurfaces of the transfer electrode array are covered with thelight-shielding layer, and the transparent layer showing an oxidizingproperty at the time of film formation is formed on the photo-electricconversion parts and the light-shielding layer.

FIGS. 9A to 9F are schematic sectional views illustrating a related-artprocess for forming a light-shielding layer covering a transferelectrode array. A photo-electric conversion portion array including aplurality of photo-electric conversion parts and the transfer electrodearray 114 including a plurality of transfer electrodes are provided inparallel to each other on a semiconductor substrate. The extendingdirection of the photo-electric conversion portion array and thetransfer electrode array is the direction orthogonal to the sheetsurface of the drawings. As shown in the figures, the height of thesurfaces of the photo-electric conversion parts 112 on the semiconductorsubstrate is roughly the same as the height of the bottom surfaces ofthe transfer electrode array 114, so that the side wall surfaces of thetransfer electrode array 114 covered with a light-shielding layer 116are rising on both sides of the photo-electric conversion part 112. Inthe process of forming the light-shielding layer illustrated in FIGS. 9Ato 9F, the material of the light-shielding layer 116 is tungsten (W). Onthe semiconductor substrate provided with the photo-electric conversionportion array and the transfer electrode array 114, the W layer 116 isfirst formed (FIG. 8A). Next, after an SiO₂ layer as a backanti-reflection coat (BARC) is formed on the surface of the W layer 116if needed, a photoresist material layer is formed, and the photoresistmaterial layer is patterned, to form a photoresist mask 140 (FIG. 8B).Subsequently, anisotropic etching is conducted by use of the photoresistmask 140 as an etching mask, whereby tungsten covering the surfaces ofthe photo-electric conversion parts 112 is removed, to form openings 118(FIG. 8C). The light-shielding layer 116 thus completed has aconfiguration in which edge portions 116 a projecting largely from thelower ends of the side wall surfaces of the transfer electrode array 114toward the photo-electric conversion parts 112 are formed at peripheraledges of the openings 118 formed in the light-shielding layer 116 incorrespondence with the photo-electric conversion parts 112. Accordingto the projection of the edge portions 116 a, the aperture areas of thephoto-electric conversion parts 112 are reduced, leading to a loweringin sensitivity.

FIGS. 9D and 9E illustrate a modified example of the above-describedprocess. In the patterning, the size of the opening 142 formed in thephotoresist material layer by the patterning is set to be equal to thespacing between the side wall surfaces of the transfer electrode array114 mutually oppositely provided on both sides of the photo-electricconversion part 112, whereby formation of the edge portion 116 a isobviated, and the aperture area of the photo-electric conversion part112 is maximized. In this case, if misalignment in the patterning is notpresent at all, formation of the edge portion is completely precluded asshown in FIG. 9E, and all the problems are solved. In practice, however,the misalignment in the patterning of the photoresist mask isinevitable; due to the misalignment, as shown in FIG. 9F, the thicknessof the light-shielding layer 116 covering the side wall surface on oneside of the transfer electrode array 114 is reduced, thereby loweringthe light shielding performance. Therefore, the edge portion 116 a ofthe light-shielding layer 116 projecting largely toward thephoto-electric conversion part 112 as shown in FIG. 9C has been anindispensable one as a method of providing a margin for absorbing themisalignment in the patterning of the photoresist mask, in therelated-art process of forming the light-shielding layer. Then, thereduction in the aperture area of the photo-electric conversion parts112 and the lowering in sensitivity, arising from the formation of suchan edge portion 116 a, have been the problems to which we could not butsubmit.

Thus, there is another need to ensure that the misalignment inpatterning of a photoresist mask can be absorbed, without forming anyedge portion projecting largely from the lower end of a side wallsurface of a transfer electrode array toward a photo-electric conversionpart at peripheral edges of the openings formed in a light-shieldinglayer in correspondence with the photo-electric conversion parts, andthat the reduction in the aperture area of the photo-electric conversionparts and the lowering of sensitivity can be thereby obviated, inmanufacturing a solid state imaging device in which the photo-electricconversion portion array including a plurality of photo-electricconversion parts and the transfer electrode array including a pluralityof transfer electrodes are provided in parallel to each other, and theupper surfaces and side wall surfaces of the transfer electrode arrayare covered with the light-shielding layer provided with the openingscorresponding to the photo-electric conversion parts.

In order to fulfill the above-mentioned need, according to an embodimentof the present invention, there is provided a method of manufacturing asolid state imaging device having a photo-electric conversion portionarray including a plurality of photo-electric conversion parts and atransfer electrode array including a plurality of transfer electrodes,the photo-electric conversion portion array and the transfer electrodearray being provided in parallel to each other, upper surfaces and sidewall surfaces of the transfer electrode array being covered with alight-shielding layer, and a transparent layer showing an oxidizingproperty at the time of film formation, the transparent layer beingformed on the photo-electric conversion parts and the light-shieldinglayer, wherein the method includes the steps of: forming alight-shielding layer material layer on a semiconductor substrateprovided with the photo-electric conversion portion array and thetransfer electrode array; forming an etching mask on the light-shieldinglayer material layer, and etching the light-shielding layer materiallayer so as to provide the light-shielding layer material layer withopenings corresponding to the photo-electric conversion parts; formingan anti-oxidizing passivation layer on the photo-electric conversionparts and the light-shielding layer; and forming the transparent layeron the passivation layer.

According to another embodiment of the present invention, there isprovided a method of manufacturing a solid state imaging device having aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, the photo-electric conversionportion array and the transfer electrode array being provided inparallel to each other, upper surfaces and side wall surfaces of thetransfer electrode array being covered with a light-shielding layer, anda transparent layer showing an oxidizing property at the time of filmformation, the transparent layer being formed on the photo-electricconversion parts and the light-shielding layer, wherein the methodincludes the steps of: forming a light-shielding layer material layer ona semiconductor substrate provided with the photo-electric conversionportion array and the transfer electrode array; forming a hard maskmaterial layer on the light-shielding layer material layer; forming anetching mask on the hard mask material layer, and etching the hard maskmaterial layer so as to provide the hard mask material layer withopenings corresponding to the photo-electric conversion parts, therebyforming a hard mask; subjecting the light-shielding layer material layerto anisotropic etching by use of the hard mask as an etching mask so asto provide the light-shielding layer material layer with openingscorresponding to the photo-electric conversion parts, thereby formingthe light-shielding layer; forming an anti-oxidizing passivation layeron the hard mask, the photo-electric conversion parts, and thelight-shielding layer exposed on the lower side of lower end portions ofthe hard mask; and forming the transparent layer on the passivationlayer.

According to a further embodiment of the present invention, there isprovided a solid state imaging device having a photo-electric conversionportion array including a plurality of photo-electric conversion partsand a transfer electrode array including a plurality of transferelectrodes, the photo-electric conversion portion array and the transferelectrode array being provided in parallel to each other, upper surfacesand side wall surfaces of the transfer electrode array being coveredwith a light-shielding layer, and a transparent layer showing anoxidizing property at the time of film formation, the transparent layerbeing formed on the photo-electric conversion parts and thelight-shielding layer, wherein an anti-oxidizing passivation layer isformed between the light-shielding layer and the photo-conducive film.

According to yet another embodiment of the present invention, there isprovided a solid state imaging device having a photo-electric conversionportion array including a plurality of photo-electric conversion partsand a transfer electrode array including a plurality of transferelectrodes, the photo-electric conversion portion array and the transferelectrode array being provided in parallel to each other, upper surfacesand side wall surfaces of the transfer electrode array being coveredwith a light-shielding layer, and a transparent layer showing anoxidizing property at the time of film formation, the transparent layerbeing formed on the photo-electric conversion parts and thelight-shielding layer, wherein surfaces of portions covering uppersurfaces of the transfer electrode array and portions covering upperregions of side wall surfaces of the transfer electrode array, of thelight-shielding layer, are covered with a hard mask formed as an etchingmask to be used in providing the light-shielding layer with openingscorresponding to the photo-electric conversion parts by anisotropicetching; and an anti-oxidizing passivation layer is formed betweensurfaces of portions not covered with the hard mask, of thelight-shielding layer, and the transparent layer, and between thesurface of the hard mask and the transparent layer.

According to a yet further embodiment of the present invention, there isprovided a camera using a solid state imaging device having aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, the photo-electric conversionportion array and the transfer electrode array being provided inparallel to each other, upper surfaces and side wall surfaces of thetransfer electrode array being covered with a light-shielding layer, anda transparent layer showing an oxidizing property at the time of filmformation, the transparent layer being formed on the photo-electricconversion parts and the light-shielding layer, wherein ananti-oxidizing passivation layer is formed between the light-shieldinglayer and the transparent layer.

According to still another embodiment of the present invention, there isprovided a camera using a solid state imaging device having aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, the photo-electric conversionportion array and the transfer electrode array being provided inparallel to each other, upper surfaces and side wall surfaces of thetransfer electrode array being covered with a light-shielding layer, anda transparent layer showing an oxidizing property at the time of filmformation, the transparent layer being formed on the photo-electricconversion parts and the light-shielding layer, wherein surfaces ofportions covering upper surfaces of the transfer electrode array andportions covering upper regions of side wall surfaces of the transferelectrode array, of the light-shielding layer, are covered with a hardmask formed as an etching mask to be used in providing thelight-shielding layer with openings corresponding to the photo-electricconversion parts by anisotropic etching; and an anti-oxidizingpassivation layer is formed between surfaces of portions not coveredwith the hard mask, of the light-shielding layer, and the transparentlayer, and between the surface of the hard mask and the transparentlayer.

In the next place, in order to fulfill the above-mentioned another need,according to an embodiment of the present invention, there is provided amethod of manufacturing a solid state imaging device having aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, the photo-electric conversionportion array and the transfer electrode array being provided inparallel to each other, upper surfaces and side wall surfaces of thetransfer electrode array being covered with a light-shielding layer, anda transparent layer showing an oxidizing property at the time of filmformation, the transparent layer being formed on the photo-electricconversion parts and the light-shielding layer, wherein the process offorming the light-shielding layer includes the steps of: forming alight-shielding layer material layer on a semiconductor substrateprovided with the photo-electric conversion portion array and thetransfer electrode array; forming a hard mask material layer on thelight-shielding layer material layer; forming a photoresist materiallayer on the hard mask material layer; patterning the photoresistmaterial layer so as to provide the photoresist material layer withopenings corresponding to the photo-electric conversion parts, therebyforming a photoresist mask, in such a manner that edge portions of theopenings formed in the photoresist material layer are aligned to withinthe range of thickness of the hard mask material layer covering thesurface of the light-shielding layer material layer at the side wallsurfaces of the transfer electrode array; subjecting the hard maskmaterial layer to anisotropic etching by use of the photoresist mask asan etching mask so as to form a hard mask; and subjecting thelight-shielding material layer to anisotropic etching by use of the hardmask as an etching mask so as to provide the light-shielding layermaterial layer with the openings corresponding to the photo-electricconversion parts.

According to another embodiment of the present invention, there isprovided a solid state imaging device having a photo-electric conversionportion array including a plurality of photo-electric conversion partsand a transfer electrode array including a plurality of transferelectrodes, the photo-electric conversion portion array and the transferelectrode array being provided in parallel to each other, and uppersurfaces and side wall surfaces of the transfer electrode array beingcovered with a light-shielding layer provided with openingscorresponding to the photo-electric conversion parts, wherein surfacesof portions covering said upper surfaces of the transfer electrode arrayand portions covering said side wall surfaces of the transfer electrodearray, of the light-shielding layer, are covered with a hard mask formedas an etching mask to be used in providing the light-shielding layerwith the openings corresponding to the photo-electric conversion partsby anisotropic etching.

According to a further embodiment of the present invention, there isprovided a camera using a solid state imaging device having aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, the photo-electric conversionportion array and the transfer electrode array being provided inparallel to each other, and upper surfaces and side wall surfaces of thetransfer electrode array being covered with a light-shielding layerprovided with openings corresponding to the photo-electric conversionparts, wherein surfaces of portions covering the upper surfaces of thetransfer electrode array and portions covering said side wall surfacesof the transfer electrode array, of the light-shielding layer, arecovered with a hard mask formed as an etching mask to be used inproviding the light-shielding layer with the openings corresponding tothe photo-electric conversion parts by anisotropic etching.

According to the present invention, the light-shielding layer coveringthe upper surfaces and side wall surfaces of the transfer electrodearray are completely isolated by the anti-oxidizing passivation layerfrom the transparent layer showing an oxidizing property at the time offilm formation. Therefore, those materials which have hitherto not beenable to be used as a light-shielding layer material notwithstandingtheir high extinction coefficients because they are susceptible tooxidation can be used to form a light-shielding layer, whereby thethickness of the light-shielding layer can be largely reduced.

In addition, according to the present invention, in forming thelight-shielding layer provided with the openings corresponding to thephoto-electric conversion parts, a method of forming the openings byanisotropic etching using a photoresist mask as in the related-artmethod is not adopted; instead, a hard mask is first formed byanisotropic etching using a photoresist mask, and then the openingscorresponding to the photo-electric conversion parts are formed in thelight-shielding layer by anisotropic etching using the hard mask.Therefore, the misalignment in patterning of the photoresist mask in themanufacturing process can be absorbed by the thickness of the hard mask,without forming edge portions projecting largely from the lower ends ofside wall surfaces of the transfer electrode array toward thephoto-electric conversion parts at the peripheral edges of the openingsformed in the light-shielding layer in correspondence with thephoto-electric conversion parts. As a result, the reduction in theaperture area of the photo-electric conversion parts and the lowering insensitivity can be obviated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing an essential part of asolid state imaging device according to a first embodiment of thepresent invention;

FIG. 2 is a schematic sectional view showing an essential part of asolid state imaging device according to a second embodiment of thepresent invention;

FIGS. 3A to 3H are schematic views illustrating a main process of amethod of manufacturing a solid state imaging device according to afirst embodiment of the present invention;

FIGS. 4A to 4H are schematic views illustrating a main process of amethod of manufacturing a solid state imaging device according to asecond embodiment of the present invention;

FIG. 5 is a schematic sectional view showing an essential part of asolid state imaging device according to a third embodiment of thepresent invention;

FIGS. 6A to 6F are schematic sectional views illustrating a process offorming a light-shielding layer in a method of manufacturing a solidstate imaging device according to a third embodiment of the presentinvention;

FIGS. 7A and 7B are schematic enlarged sectional views of alight-shielding layer and a hard mask, for illustrating the processshown in FIGS. 6A to 6F;

FIGS. 8A to 8G are schematic sectional views illustrating a process offorming a light-shielding layer according to a modified example, inwhich a BARC is formed by modifying the process shown in FIGS. 6A to 6F;and

FIGS. 9A to 9F are schematic sectional views illustrating a related-artprocess of forming a light-shielding layer covering a transfer electrodearray.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, embodiments of the present invention will be described below. FIG.1 is a schematic sectional view showing an essential part of a solidstate imaging device 10 according to a first embodiment of the presentinvention, and FIG. 2 is a schematic sectional view showing an essentialpart of a solid state imaging device 10′ according to a secondembodiment of the present invention. First, common configurations of thesolid state imaging devices 10 and 10′ will be described. The solidstate imaging devices 10 and 10′ are charge coupled devices (CCD), inwhich a photo-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes are provided in parallel to eachother on a semiconductor substrate. The extending direction of thephoto-electric conversion portion array and the transfer electrode arrayis the direction orthogonal to the sheet surface of the drawings. Uppersurfaces and side wall surfaces of the transfer electrode array 14 arecovered with a light-shielding layer 16 of ruthenium (Ru), and thelight-shielding layer 16 is provided with openings 18 corresponding tothe photo-electric conversion parts 12. Incidentally, the material ofthe light-shielding layer 16 may be other material than Ru. The uppersurfaces and side wall surfaces of the transfer electrode array 14 areinsulated from the light-shielding layer 16 by a layer insulating film20, and the lower surfaces of the transfer electrode array 14 areinsulated from charge transfer paths 24 therebeneath by anotherinsulating film 22. Further, a first transparent layer 26 is formed onthe photo-electric conversion parts 12 and the light-shielding layer 16,and a second transparent layer 28 different from the first transparentlayer 26 in refractive index is formed on the first transparent layer26. A color filter layer 30 is formed on the second transparent layer28, and, further, an on-chip lens 32 is formed thereon.

The first and second transparent layers 26 and 28 are formed of boronphosphorus silicate glass (BPSG), and the compositions of the films areset different from each other so that the films have differentrefractive indices, whereby a refracting action is imparted to theinterface between them, and a lens is thereby constituted. Incidentally,the material of the transparent layers is not limited to BPSG; forexample, phosphorus silicate glass (PSG), arsenic glass (AsSG), ortetraethyl orthosilicate (TEOS)+ozone may be adopted as the material.The transparent layers formed of such a material show an oxidizingproperty at the time of film formation, and, particularly, they show astrong oxidizing property in a heating reflow step included in the filmforming process. Therefore, if the transparent layer formed of such amaterial is formed directly on the light-shielding layer 16 formed of Ruor the like material susceptible to oxidation, the light shieldingperformance of the light-shielding layer 16 might be markedly damaged.

In view of this, in the solid state imaging device 10 shown in FIG. 1,an anti-oxidizing passivation layer 34 is formed between thelight-shielding layer 16 formed of Ru and the first transparent layer 26formed of BPSG. The passivation layer 34 is preferably formed as a filmtransparent to visible rays, by use of a material not containing oxygen,such as SiN, SiC, and SiCN. In this configuration, the light-shieldinglayer 16 is completely isolated from the first transparent layer 26 bythe passivation layer 34, and, therefore, even if the first transparentlayer 26 shows a strong oxidizing property at the time of filmformation, the light shielding performance of the light-shielding layer16 is not thereby damaged at all.

On the other hand, in the solid state imaging device 10′ shown in FIG.2, the surfaces of portions covering the upper surfaces of the transferelectrode array 14, of the light-shielding layer 16, and the surfaces ofportions covering upper regions of side wall surfaces of the transferelectrode array 14, of the light-shielding layer 16, are covered with ahard mask 38. The hard mask 38 is formed as an etching mask to be usedin providing the light-shielding layer 16 with the openings 18corresponding to the photo-conversion parts 12 by anisotropic etching.As the material of the hard mask 38, for example, SiN, SiC, SiCN or thelike is used, and, further, other materials may also be used. Inaddition, the region of removing the material of the light-shieldinglayer material layer by anisotropic etching conducted using the hardmask 38 is broadened to the lower side of lower end portions of the hardmask 38 covering the surface of the light-shielding layer material layerat the side wall surfaces of the transfer electrode array 14. Thisbroadening is achieved by over-etching in conducting the anisotropicetching. As is clear from the figure, on the lower side of the lower endportions of the hard mask 38, the surface of the light-shielding layer16 is not covered with the hard mask 38; therefore, the light shieldingperformance of the light-shielding layer 16 at the non-covered portionsmay be damaged at the time of forming the first transparent layer 26. Inview of this, also in the solid state imaging device 10′ shown in FIG.2, an anti-oxidizing passivation layer 36 is formed. The passivationlayer 36 is formed between the surfaces of portions, not covered withthe hard mask 38, of the light-shielding layer 16 and the firsttransparent layer 26, and between the surface of the hard mask 38 andthe first transparent layer 26. Like the passivation layer 34 in FIG. 1,the passivation layer 36 in FIG. 2 is preferably formed as a filmtransparent to visible rays, by use of a material not containing oxygen,such as SiN, SiC, and SiCN. In this configuration, the light-shieldinglayer 16 is completely isolated from the first transparent layer 26 bythe hard mask 38 and the passivation layer 36; therefore, even if thefirst transparent layer 26 shows a strong oxidizing property at the timeof film formation, the light shielding performance of thelight-shielding layer 16 is not thereby damaged at all. Incidentally,the solid state imaging devices 10 and 10′ are provided with not onlythe above-mentioned components but also other various components forpermitting the devices to function as solid state imaging devices.However, these components are not intrinsic of the embodiments of thepresent invention, and may be provided with usual structures, and,therefore, description of these components is omitted.

As is clear from the foregoing, the solid state imaging device accordingto the embodiments of the present invention are so configured that thelight shielding performance of the light-shielding layer is preventedfrom being damage by the transparent layer which shows an oxidizingproperty at the time of film formation. Therefore, the embodiments ofthe present invention are effective always when applied to aconfiguration in which the material of a light-shielding layer mayotherwise be oxidized. For example, such metallic materials as Al, W,and Mo are not so susceptible to oxidation as Ru, but thelight-shielding layers formed of these materials may also be encounteredby the problem of degradation of light shielding performance due tooxidation, after the thinning of the film progresses further. Therefore,the embodiments of the present invention generally can display itseffects when applied to solid state imaging devices in which alight-shielding layer is formed of a metallic material. It should benoted, however, that the materials such as Ru and Ir which have hithertobeen not usable as a light-shielding layer material notwithstandingtheir high extinction coefficients because they are susceptible tooxidation are made to be usable by the embodiments of the presentinvention, and the light-shielding layer can thereby be much thinned, sothat the effects of the embodiments of the present invention areparticularly conspicuous when the embodiments of the invention areapplied to the cases where the light-shielding layer material is Ru orIr.

Furthermore, the present invention, in another state, provides variouscameras such as digital still cameras, video cameras, and cameras havingthe functions of both types of cameras, and a camera pertaining to theembodiments of the present invention is a camera using a solid stateimaging device according to the embodiments of the invention. A camerausing a solid state imaging device itself is publicly known, and,therefore, when one skilled in the art is provided with the informationabout the solid state imaging device according to the embodiments of thepresent invention, he can easily manufacture a camera according to theembodiments of the present invention, based on the information.

FIGS. 3A to 3H are schematic views illustrating a main process in themethod of manufacturing a solid state imaging device according to afirst embodiment of the present invention, and FIGS. 4A to 4H areschematic views illustrating a main process in the method ofmanufacturing a solid state imaging device according to a secondembodiment of the present invention. Of various processes constitutingthe method of manufacturing a solid state imaging device according tothe embodiments of the present invention, the other processes than theprocesses shown in these figures are not processes intrinsic of theembodiments of the invention, and may be conducted according to theusual method; therefore, description of the other processes is omitted.

The main process in the method of manufacturing a solid state imagingdevice shown in FIGS. 3A to 3H is a process in manufacturing the solidstate imaging device 10 shown in FIG. 1. As shown in FIG. 1, the heightof the surfaces of the photo-electric conversion parts 12 on thesemiconductor substrate is roughly at the same level as the height ofthe bottom surfaces of the transfer electrode array 14, so that the sidewall surfaces of the transfer electrode array 14 covered with thelight-shielding layer 16 are rising on both sides of each photo-electricconversion part 12.

In the process shown in FIGS. 3A to 3H, first, for forming thelight-shielding layer 16, a film of ruthenium (Ru) is formed on thesemiconductor substrate provided with the photo-electric conversionarray and the transfer electrode array, to form a light-shielding layermaterial layer (Ru layer) 16 (FIG. 3A). The forming of the Ru layer 16may be conducted by sputtering, CVD or the like. Next, a photoresistmask 40 provided with openings 42 corresponding to the photo-electricconversion parts 12 is formed on the Ru layer 16 (FIG. 3B).Subsequently, anisotropic etching is applied to the Ru layer 16 by useof the photoresist mask 40 as an etching mask, to provide the Ru layer16 with openings 18 corresponding to the photo-electric conversion parts12. As a result, the light-shielding layer 16 is completed.Subsequently, ashing is conducted to remove the photoresist mask 40(FIG. 3C).

Next, an anti-oxidizing passivation layer 34 is formed on thephoto-electric conversion parts 12 and the light-shielding layer 16(FIG. 3D). The passivation layer 34 is preferably formed from a materialnot containing oxygen, such as SiN, SiC and SiCN. In addition, thepassivation layer is preferably formed as a film transparent to visiblerays, and may be formed by use of sputtering, CVD or the like method.Subsequently, a photoresist mask 44 having openings 46 corresponding tothe photo-electric conversion parts 12 is formed on the passivationlayer 34 (FIG. 3E). Next, anisotropic etching is applied to thepassivation layer 34 by use of the photoresist mask 44 as an etchingmask, to provide the passivation layer 34 with openings 48 correspondingto the photo-electric conversion parts 12 (i.e., the passivation layer34 on the surfaces of the photo-electric conversion parts 12 isremoved). Subsequently, ashing is conducted to remove the photoresistmask 44 (FIG. 3F). Thereafter, a first transparent layer 26 composed ofBPSG or the like material is formed on the passivation layer 34 (FIG.3G). Incidentally, in the above description, the removal of thepassivation layer 34 present on the surfaces of the photo-electricconversion parts 12 is to reduce the number of interfaces between filmsdiffering in refractive index, to thereby reduce the reflection on theinterfaces, and to increase the amount of light incident on thephoto-electric conversion parts 12. However, where the reflection on theinterface is so slight that it imposes no problem, the removing step maybe omitted, and the formation of a first transparent layer 26 (FIG. 3H)may be conducted immediately from the condition of FIG. 3D.

The main process in the method of manufacturing a solid state imagingdevice shown in FIGS. 4A to 4H is a process in manufacturing the solidstate imaging device 10′ shown in FIG. 2. As shown in FIG. 2, the heightof the surfaces of the photo-electric conversion parts 12 on thesemiconductor substrate is roughly at the same level as the height ofthe bottom surfaces of the transfer electrode array 14, so that sidewall surfaces of the transfer electrode array 14 covered with thelight-shielding layer 16 are rising on both sides of each photo-electricconversion part 12.

In the process illustrated in FIGS. 4A to 4H, first, for forming thelight-shielding layer 16, a film of ruthenium (Ru) is formed on thesemiconductor substrate provided with the photo-electric conversionportion array and the transfer electrode array, to form alight-shielding layer material layer (Ru layer) 16 (FIG. 4A). Theforming of the Ru layer 16 may be conducted by use of sputtering, CVD orthe like method. Next, an SiN layer 50 is formed on the Ru layer 16. TheSiN layer 50 is formed for forming a hard mask 38, and is therefore ahard mask material layer. The forming of the SiN layer 50 may also beconducted by sputtering, CVD or the like method. Subsequently, aphotoresist mask 40 having openings 42 corresponding to thephoto-electric conversion parts 12 is formed (FIG. 4B).

Next, anisotropic etching is applied to the SiN layer 50 by use of thephotoresist mask 40 as an etching mask, to provide the SiN layer 50 withopenings corresponding to the photo-electric conversion parts 12,whereby the hard mask 38 is completed. Subsequently, ashing is conductedto remove the photoresist mask 40. Furthermore, anisotropic etching isapplied to the Ru layer 16 by use of the hard mask 38 as an etchingmask, to provide the Ru layer 16 with openings 18 corresponding to thephoto-electric conversion parts 12, whereby the light-shielding layer 16is completed. The anisotropic etching applied to the Ru layer 16 ispreferably conducted by impressing a bias voltage on a lower electrodein a dry etching apparatus while using a mixed gas containing Cl, CF₂,Ar or the like as an etching gas. The anisotropic etching applied to theRu layer 16 is for cutting the Ru layer 16 by use of the hard mask 38 asan etching mask, so that the shape of the openings 18 thus formed isobtained through transfer of the corresponding shape of the hard mask38. It is to be noted, however, that it is preferable that theanisotropic etching is not stopped upon transfer of the shape butfurther continued (i.e., over-etching is conducted). This ensures thateven if the application of the bias voltage is being continued, asufficient amount of the etching gas is supplied to the lower side ofthe lower end portions of the hard mask 38, so that the Ru layer 16 inthese regions can also be cut and removed. Therefore, by conductingover-etching, as shown in FIG. 4C, the region of removing the materialof the Ru layer 16 by anisotropic etching can be broadened to the lowerside of the lower end portions of the hard mask 38 covering the surfaceof the W layer 16 at side wall surfaces of the transfer electrode array14.

Next, an anti-oxidizing passivation layer 36 is formed on the hard mask38, the photo-electric conversion parts 12, and the light-shieldinglayer 16 exposed on the lower side of the lower end portions of the hardmask 38 (FIG. 4D). The passivation layer 36 is preferably formed of amaterial not containing oxygen, such as SiN, SiC, and SiCN. In addition,the passivation layer 36 is preferably formed as a film transparent tovisible rays, and may be formed by use of sputtering, CVD or the likemethod. Subsequently, a photoresist mask 44 provided with openings 46corresponding to the photo-electric conversion parts 12 is formed on thepassivation layer 36 (FIG. 4E). Next, anisotropic etching is applied tothe passivation layer 34 by use of the photoresist mask 44 as an etchingmask, to provide the passivation layer 36 with openings 52 correspondingto the photo-electric conversion parts 12 (i.e., the passivation layer36 on the surfaces of the photo-electric conversion parts 12 isremoved). Here, also, the region of removing the material of thepassivation layer 36 by anisotropic etching is preferably broadened tothe outer side by conducting over-etching, whereby the aperture area ofthe photo-electric conversion parts 12 is increased, leading to anenhanced sensitivity. Besides, with the openings 52 broadened,diffraction of light is suppressed, so that smear characteristic is alsoimproved. Subsequently, ashing is conducted to remove the photoresistmask 44 (FIG. 4F). Thereafter, a first transparent layer 26 composed ofBPSG or the like is formed on the passivation layer 36 (FIG. 4G).Incidentally, like in the process shown in FIG. 3, the step of removingthe passivation layer 36 on the surfaces of the photo-electricconversion parts 12 may be omitted, and the formation of the firsttransparent layer 26 (FIG. 4H) may be conducted immediately from thecondition of FIG. 4D.

As has been described above, according to the embodiments of the presentinvention, the light-shielding layer 16 covering the upper surfaces andside wall surfaces of the transfer electrode array 14 is completelyisolated from the transparent layer 26 showing an oxidizing property atthe time of film formation, by the anti-oxidizing passivation layers 34and 36. Therefore, those materials which have hitherto been not usableas a light-shielding layer material notwithstanding their highextinction coefficients because they are susceptible to oxidation can beused, so that the thickness of the light-shielding layer can be muchreduced.

Now, a third embodiment of the present invention will be described. FIG.5 is a schematic sectional view showing an essential part of a solidstate imaging device 10 according to the third embodiment of the presentinvention. The solid state imaging device 10 as shown is a chargecoupled device (CCD), in which a photo-electric conversion portion arrayincluding a plurality of photo-electric conversion parts and a transferelectrode array including a plurality of transfer electrodes areprovided in parallel to each other on a semiconductor substrate. Theextending direction of the photo-electric conversion portion array andthe transfer electrode array is the direction orthogonal to the sheetsurface of the drawing. Upper surfaces and side wall surfaces of thetransfer electrode array 14 are covered with a light-shielding layer 16′of tungsten (W), and the light-shielding layer 16′ is provided withopenings 18 corresponding to the photo-electric conversion parts 12.Incidentally, the material of the light-shielding layer 16′ may be othermaterial than W. The upper surfaces and side wall surfaces of thetransfer electrode array 14 are insulated from the light-shielding layer16′ by a layer insulating film 20, and the lower surfaces of thetransfer electrode array 14 are insulated from charge transfer paths 24therebeneath by another layer insulating film 22. Furthermore, a firsttransparent layer 26 is formed on the photo-electric conversion parts 12and the light-shielding layer 16′, and a second transparent layer 28differing from the first transparent layer 26 in refractive index isformed on the first transparent layer 26. A color filter layer 30 isformed on the second transparent layer 28, and, further, an on-chip lens32 is formed thereon. The first and second transparent layers 26 and 28are formed of boron phosphorus silicate glass (BPSG), and by setting thecompositions of both films to be different and thereby setting therefractive indices of the films to be different, a refractive action isimparted to the interface between the films, to thereby constitute alens. Incidentally, the material of these transparent layers is notlimited to BPSG; for example, phosphorus silicate glass (PSG), arsenicglass (AsSG), tetraethyl orthosilicate (TEOS)+ozone or the like may alsobe used. In addition, in order to set the interface between the films ina desired shape, it suffices, for example, to conduct a heating reflowstep in forming the first transparent layer 26.

As is clear from the figures, the surfaces of portions covering theupper surfaces of the transfer electrode array 14, of thelight-shielding layer 16′, and the surfaces of portions covering upperregions of the side wall surfaces of the transfer electrode array 14, ofthe light-shielding layer 16′, are covered with the hard mask 38, andthe hard mask 38 is formed as an etching mask to be used in providingthe light-shielding layer 16′ with the openings 18 corresponding to thephoto-electric conversion parts 12 by anisotropic etching. As thematerial of the hard mask 38, for example, SiO₂, SiN, SiON or the likeis used. In addition, the region of removing the material of thelight-shielding layer material layer by anisotropic etching using thehard mask 38 is broadened to the lower side of lower end portions of thehard mask 38 covering the surface of the light-shielding layer materiallayer at the side wall surfaces of the transfer electrode array 14. Thisbroadening is achieved by conducting over-etching in carrying out theanisotropic etching. Incidentally, the solid state imaging device 10 isprovided not only with the above-mentioned components but also withother various components for permitting the device to function as asolid state imaging device. The other components are not intrinsic ofthe embodiments of the present invention, and may be provided with theusual structures, and, therefore, description of the other components isomitted.

Furthermore, the embodiments of the present invention, in another state,provides various cameras such as digital still cameras, video cameras,and cameras having the functions of both types of cameras, and a camerapertaining to the embodiments of the present invention is a camera usinga solid state imaging device according to the invention. A camera usinga solid state imaging device itself is publicly known, and, therefore,when one skilled in the art is provided with the information about thesolid state imaging device according to the embodiments of the presentinvention, he can easily manufacture a camera according to theembodiments of present invention, based on the information.

FIGS. 6A to 6F are schematic sectional views illustrating a process offorming a light-shielding layer in a method of manufacturing a solidstate imaging device according to a third embodiment of the presentinvention, and FIGS. 7A and 7B are schematic enlarged sectional views ofa light-shielding layer and a hard mask, for illustrating the processshown in FIGS. 6A to 6F. Of various processes constituting the method ofmanufacturing a solid state imaging device according to the embodimentsof the present invention, the other processes than the process offorming a light-shielding layer are processes not intrinsic of theinvention, and may be conducted according to the usual methods, and,therefore, description of the other processes is omitted.

The process of forming a light-shielding layer shown in FIGS. 6A to 6Fis a process for forming the light-shielding layer 16′ in the solidstate imaging device 10 shown in FIG. 5. As shown in FIG. 5, the heightof the surfaces of photo-electric conversion parts 12 on thesemiconductor substrate is roughly at the same level as the height ofthe bottom surfaces of the transfer electrode array 14, so that sidewall surfaces of the transfer electrode array 14 covered with thelight-shielding layer 16′ are rising on both side of each photo-electricconversion part 12.

In the process shown in FIGS. 6A to 6F, first, for forming thelight-shielding layer 16′, a film of tungsten (W) as a light-shieldinglayer material is formed on the semiconductor substrate provided withthe photo-electric conversion portion array and the transfer electrodearray, to form a light-shielding layer material layer (W layer) 16′(FIG. 6A). The forming of the W layer 16′ may be conducted bysputtering, CVD or the like method. Incidentally, the materials whichcan be used for forming the light-shielding layer 16′ include not only Wbut also various metallic materials such as Mo, Ta, Pt, Ru, Ir, Al, Ti,etc., alloys, and nitride or oxygen compounds thereof and the like.

Next, an SiO₂ layer 36′ is formed on the W layer 16′ (FIG. 6B). The SiO₂layer 36′ is for forming a hard mask 38, and is therefore a hard maskmaterial layer. The use of SiO₂ as the material of the hard mask 38 isbased on the fact that the etching selectivity ratio of SiO₂ to W can behigh preferably, in applying anisotropic etching to the W layer 16′ byuse of a dry etching apparatus as will be described later. It is to benoted, however, SiN, SiON and the like can also be used as the materialof the hard mask 38. In addition, any other material can also be usedinasmuch as the etching selectivity ratio of the material to W can behigh and a film of the material can be formed conformally on the W layer16′ by CVD or the like method.

The thickness of the hard mask 38 (hence, the thickness of the SiO₂layer 36′ formed as the hard mask material layer) is determinedaccording to such factors as accuracy of patterning applied to aphotoresist material layer to be described later, the etchingselectivity ratio of SiO₂ to W, etc., and this will be described indetail later.

Next, a photoresist material layer is formed on the hard mask materiallayer 36′, the photoresist material layer is patterned byphotolithography to provide the photoresist material layer with openings42 corresponding to the photo-electric conversion parts 12, to form aphotoresist mask 40 (FIG. 6C). Besides, in the patterning, as shown inFIG. 7A, an alignment is conducted such that an edge portion R of theopening 42 formed in the photoresist material layer is set within therange of the thickness T of the hard mask material layer 36′ coveringthe surface of the W layer 16′ at the side wall surface of the transferelectrode array 14. Misalignment in patterning of the photoresist maskis inevitable; however, according to this aligning step, it sufficesthat the edge portion R of the opening 42 formed in the photoresistmaterial layer is located within the range of the thickness T of thehard mask material layer 36′ covering the surface of the W layer 16′ atthe side wall surface of the transfer electrode array 14, so that theaccuracy required in the patterning of the photoresist mask 40 is low,and such a level of alignment can be carried out easily and assuredly.Upon such an alignment, the hard mask material layer 36′ is configuredas shown in FIG. 7A, in which of the range of the thickness T thereofcovering the surface of the W layer 16′ at the side wall surface of thetransfer electrode array 14, only the portion OT on the face side isexposed from the photoresist mask 40, and the portion IT on the innerside (the W layer 16′ side) is covered with the photoresist 40.

Subsequently, anisotropic etching is applied to the hard mask materiallayer 36′ by use of the photoresist mask 40 as an etching mask, to forma hard mask 38 (FIG. 6D). In this instance, the etching amount of thehard mask material layer 361 is set at such a level as to be necessaryfor removing the thickness portion of the hard mask material layer 36′covering the surface of the photo-electric conversion part 12. As aresult, as shown in FIG. 7B, of the hard mask material layer 36′, theportion OT exposed from the photoresist mask 40 is cut away over aheight H roughly corresponding to the hard mask material layer 36′covering the surface of the photo-electric conversion part 12. However,since the height of the side wall surface of the transfer electrodearray 14 is sufficiently larger than the height H of the portion cutaway, the lower end portion of the hard mask 38 can retain its originalshape, without being cut away by the anisotropic etching.

Next, by use of the thus-formed hard mask 38 as an etching mask,anisotropic etching is applied to the W layer 16′ present as thelight-shielding layer material layer, to provide the W layer 16′ withopenings 18 corresponding to the photo-electric conversion parts 12(FIG. 6E). The anisotropic etching applied to the W layer 16′ ispreferably conducted by applying a bias voltage to a lower electrode ofa dry etching apparatus while using a mixed gas of Cl, CF₂, Ar or thelike as an etching gas; however, an etching gas in which O₂, N₂ or thelike is mixedly present may also be used without any problem. Since theanisotropic etching applied to the W layer 16′ is an etching for cuttingthe W layer 16′ by using the hard mask 38 as an etching mask, the shapeof the openings 18 thus formed have a shape obtained by transfer of theshape of the hard mask 38. Moreover, the shape of the hard mask 38 thustransferred is the shape of the lower end portions of the hard mask 38,which is maintained without being cut by the anisotropic etchingconducted for forming the hard mask 38. Therefore, though misalignmentin the patterning of the photoresist mask 40 is inevitable, the shape,size and positions of the openings 18 formed in the light-shieldinglayer 16′ by the above-mentioned process are completely relieved fromthe influence of the misalignment, so that the openings 18 in thelight-shielding layer 16′ can be formed with high accuracy.

Furthermore, when the anisotropic etching is continued after the removalof the W layer 16′ present on the surfaces of the photo-electricconversion parts 12 (over-etching is conducted), a sufficient amount ofthe etching gas is supplied to the lower side of the lower end portionsof the hard mask 38 even if the application of the bias voltage iscontinued, so that the W layer 16′ in these regions can also be cut awayand removed. Therefore, by conducting the over-etching, as shown in FIG.6E, the region of removing the W layer 16′ by the anisotropic etchingcan be broadened to the lower side of the lower end portions of the hardmask 38 covering the surface of the W layer 16′ at side wall surfaces ofthe transfer electrode array 14. As a result, the size of the openings18 can be uniformly enlarged without disordering the shape of theopenings 18, so that the aperture area of the openings 18 is increased,leading to an enhanced sensitivity. In addition, since diffraction oflight is suppressed by the broadening of the openings 18, smearcharacteristic is also improved. When the light-shielding layer 16′ iscompleted in the above-mentioned manner, ashing is subsequentlyconducted, to remove the photoresist mask (FIG. 6F).

Here, the thickness of the hard mask 38 (hence, the thickness of theSiO₂ layer 36, formed as the hard mask material layer) will be describedmore in detail. The method of manufacturing a solid state imaging deviceaccording to an embodiment of the present invention is a method in whichthe misalignment in patterning of a photoresist is brought to within therange of the thickness T of the hard mask material layer 36′ coveringthe surface of the W layer 16′ at side wall surfaces of the transferelectrode array 14, whereby the misalignment is absorbed. Therefore, asthe thickness T of the hard mask material layer 36′ is set larger, themargin for the misalignment can be made greater. However, when thethickness T is too large, the etching time in removing the W layer 16′to the lower side of the lower ends of the hard mask 38 becomes long,and the shape of the opening 18 formed in the light-shielding layer 16′is thereby disordered, unfavorably. The magnitude of the misalignmentdepends mainly on the performance of the exposure machine used inlithography, while the etching time and the shape of the openings formeddepend mainly on the performance of the etching apparatus. Therefore, inconsideration of the performances of the exposure machines and theetching apparatuses in general use at present, the thickness of the hardmask 38 is desirably in the range of about 40 to 120 nm.

It is to be noted, however, the thickness of the hard mask 38 mayconstitute a factor for narrowing the aperture area of thephoto-electric conversion parts 12, and, therefore, it is preferable toset the thickness as small as possible, for enhancing the performance ofthe solid state imaging device 10. In order to reduce the thickness ofthe hard mask 38, it is desirable to suppress the misalignment inpatterning of the photoresist mask. For this purpose, a backanti-reflection coat (BARC) may be formed on the hard mask materiallayer 36′ and the photoresist material layer may be formed thereon,whereby light reflection and its scattering at the time of lightexposure can be suppressed by the BARC, so that a misalignment-reducingeffect is obtained. FIGS. 8A to 8G are schematic sectional viewsillustrating a process of forming a light-shielding layer according to amodified embodiment, in which a modification consisting in forming theBARC is applied to the process shown in FIGS. 6A to 6F.

In the process illustrated in FIGS. 8A to 8G, first, a W layer 16′ as alight-shielding layer material layer is formed on a semiconductorsubstrate provided with a photo-electric conversion portion array and atransfer electrode array 14 (FIG. 8A). Incidentally, the material of thelight-shielding layer 16′ may be other material than W. Next, a hardmask material layer 36′ is formed on the W layer 16′, a BARC 44 isformed on the hard mask material layer 36′, and further a photoresistmaterial layer is formed thereon. Then, the photoresist material layeris patterned by photolithography, to provide the photoresist materiallayer with openings 42 corresponding to the photo-electric conversionparts 12, thereby forming a photoresist mask 40 (FIG. 8B). Besides, inthe patterning, like in the process of FIGS. 6A to 6F, an alignment isconducted such that edge portions of the openings 42 to be formed in thephotoresist material layer are brought to within the range of thethickness of the hard mask material layer 36′ covering the surface ofthe W layer 16′ at side wall surfaces of the transfer electrode array14.

Next, using the photoresist mask 40 as an etching mask, the BARC 44 isetched, to thereby remove the exposed portions of the BARC 44 (FIG. 8C).Furthermore, using the photoresist mask 40 as an etching mask,anisotropic etching is applied to the hard mask material layer 36′, tothereby form a hard mask 38 (FIG. 8D). Subsequently, using the thusformed hard mask 38 as an etching mask, anisotropic etching is appliedto the W layer 16′ present as a light-shielding layer material layer, toprovide the W layer 16′ with openings 18 corresponding to thephoto-electric conversion parts 12 (FIG. 8E). The anisotropic etchingapplied to the W layer 16′ may be conducted in the same manner as in theprocess of FIGS. 6A to 6F. Further, after the removal of the W layer 16′present on the surfaces of the photo-electric conversion parts 12, theanisotropic etching is continued (over-etching is conducted), wherebythe region of removing the W layer 16′ by the anisotropic etching isbroadened to the lower side of lower end portions of the hard mask 38covering the surface of the W layer 16′ at side wall surfaces of thetransfer electrode array 14, as shown in FIG. 8F. When thelight-shielding layer 16′ is completed in this manner, ashing issubsequently conducted to remove the BARC and the photoresist (FIG. 8G).

As has been described above, according to the embodiments of the presentinvention, in providing the light-shielding layer 16′ with the openings18 corresponding to the photo-electric conversion parts 12, a method offorming the openings by anisotropic etching conducted using aphotoresist mask as in the related-art method is not adopted, but,instead, the hard mask 38 is formed by anisotropic etching conducted byuse of a photoresist mask, and the openings 18 corresponding to thephoto-electric conversion parts 12 are formed in the light-shieldinglayer 16′ by anisotropic etching conducted using the hard mask 38.Therefore, the misalignment in patterning of the photoresist mask in themanufacturing process can be absorbed by the thickness of the hard mask38, without formation of edge portions projecting largely from the lowerends of side wall surfaces of the transfer electrode array 14 toward thephoto-electric conversion parts 12, at the peripheral edges of theopenings 18 formed in the light-shielding layer 16′ in correspondencewith the photo-electric conversion parts 12. This makes it possible toobviate a reduction in the aperture area of the photo-electricconversion parts and a lowering in sensitivity. In addition, inproviding the light-shielding layer 16′ with the openings 18corresponding to the photo-electric conversion parts 12 by theanisotropic etching conducted by use of the hard mask 38, over-etchingis conducted, whereby the region of removing the material of thelight-shielding layer material layer by the anisotropic etching can bebroadened to the lower side of the lower end portions of the hard mask38 covering the surface of the light-shielding layer material layer atside wall surfaces of the transfer electrode array 14. As a result, thesize of the openings 18 can be uniformly enlarged without disorderingthe shape of the openings 18, so that the aperture area of thephoto-electric conversion parts 12 is increased, leading to an enhancedsensitivity. In addition, the broadening of the openings reduces thediffracted light, whereby leakage of light into transfer channels issuppressed, and smear characteristic is improved.

While preferred embodiments of the present invention have been describedusing specific terms, such description is for illustrative purpose only,and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

1. A method of manufacturing a solid state imaging device comprising aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, said photo-electric conversionportion array and said transfer electrode array being provided inparallel to each other, upper surfaces and side wall surfaces of saidtransfer electrode array being covered with a light-shielding layer, anda transparent layer showing an oxidizing property at the time of filmformation, said transparent layer being formed on said photo-electricconversion parts and said light-shielding layer, wherein the process offorming said light-shielding layer comprises the steps of forming alight-shielding layer material layer on a semiconductor substrateprovided with said photo-electric conversion portion array and saidtransfer electrode array; forming a hard mask material layer on saidlight-shielding layer material layer; forming a photoresist materiallayer on said hard mask material layer; patterning said photoresistmaterial layer so as to provide said photoresist material layer withopenings corresponding to said photo-electric conversion parts, therebyforming a photoresist mask, in such a manner that edge portions of saidopenings formed in said photoresist material layer are aligned with saidhard mask material layer covering said light-shielding layer materiallayer at said side wall surfaces of said transfer electrode array;subjecting said hard mask material layer to anisotropic etching by useof said photoresist mask as an etching mask so as to form a hard mask;and subjecting said light-shielding material layer to anisotropicetching by use of said hard mask as an etching mask so as to providesaid light-shielding layer material layer with said openingscorresponding to said photo-electric conversion parts.
 2. The method ofmanufacturing a solid state imaging device as set forth in claim 1,wherein in said anisotropic etching of said light-shielding layermaterial layer, over-etching is conducted, whereby the region of removalof the material of said light-shielding layer material layer by saidanisotropic etching is broadened to the lower side of lower end portionsof said hard mask covering the surface of said light-shielding layermaterial layer at said side wall surfaces of said transfer electrodearray.
 3. The method of manufacturing a solid state imaging device asset forth in claim 1, wherein in forming said photoresist material layeron said hard mask material layer, a back anti-reflection film is formedon said hard mask material layer, and said photoresist material layer isformed thereon.
 4. The method of manufacturing a solid state imagingdevice as set forth in claim 1, wherein SiO₂, SiN, or SiON is used as amaterial of said hard mask.
 5. A solid state imaging device comprising aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, said photo-electric conversionportion array and said transfer electrode array being provided inparallel to each other, and upper surfaces and side wall surfaces ofsaid transfer electrode array being covered with a light-shielding layerprovided with openings corresponding to said photo-electric conversionparts, wherein surfaces of portions covering said upper surfaces of saidtransfer electrode array and portions covering said side wall surfacesof said transfer electrode array, and of said light-shielding layer, arecovered with a hard mask formed as an etching mask to be used inproviding said light-shielding layer with said openings corresponding tosaid photo-electric conversion parts by anisotropic etching, wherein thehard mask does not extend to lowest portions of the light shieldinglayer.
 6. The solid state imaging device as set forth in claim 5,wherein the region of removal of the material of said light-shieldinglayer material layer by said anisotropic etching is broadened to thelower side of lower end portions of said hard mask covering the surfaceof said light-shielding layer material layer at said side wall surfacesof said transfer electrode array.
 7. A solid state imaging device as setforth in claim 5, wherein said hard mask is formed of SiO₂, SiN, orSiON.
 8. A camera using a solid state imaging device comprising aphoto-electric conversion portion array including a plurality ofphoto-electric conversion parts and a transfer electrode array includinga plurality of transfer electrodes, said photo-electric conversionportion array and said transfer electrode array being provided inparallel to each other, and upper surfaces and side wall surfaces ofsaid transfer electrode array being covered with a light-shielding layerprovided with openings corresponding to said photo-electric conversionparts, wherein surfaces of portions covering said upper surfaces of saidtransfer electrode array and portions covering said side wall surfacesof said transfer electrode array, and of said light-shielding layer, arecovered with a hard mask formed as an etching mask to be used inproviding said light-shielding layer with said openings corresponding tosaid photo-electric conversion parts by anisotropic etching, wherein thehard mask does not extend to lowest portions of the light shieldinglayer.
 9. The camera using a solid state imaging device as set forth inclaim 8, wherein the region of removal of the material of saidlight-shielding layer material layer by said anisotropic etching isbroadened to the lower side of lower end portions of said hard maskcovering the surface of said light-shielding layer material layer atsaid side wall surfaces of said transfer electrode array.
 10. The camerausing a solid state imaging device as set forth in claim 8, wherein saidhard mask is formed of SiO₂, SiN, or SiON.